In a typical wireless communication network, wireless devices, also known as wireless communication devices, mobile stations, stations (STA) and/or user equipments (UE), communicate via a Radio Access Network (RAN) to one or more core networks. The RAN covers a geographical area which is divided into service areas or cell areas, with each service area or cell area being served by a radio network node such as a radio access node e.g., a Wi-Fi access point or a radio base station (RBS), which in some networks may also be denoted, for example, a “NodeB” or “eNodeB”. The area or cell area is a geographical area where radio coverage is provided by the radio network node. The radio network node communicates over an air interface operating on radio frequencies with the wireless device within range of the radio network node.
A Universal Mobile Telecommunications System (UMTS) is a third generation telecommunication network, which evolved from the second generation (2G) Global System for Mobile Communications (GSM). The UMTS terrestrial radio access network (UTRAN) is essentially a RAN using wideband code division multiple access (WCDMA) and/or High Speed Packet Access (HSPA) for user equipments. In a forum known as the Third Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for third generation networks, and investigate enhanced data rate and radio capacity. In some RANs, e.g. as in UMTS, several radio network nodes may be connected, e.g., by landlines or microwave, to a controller node, such as a radio network controller (RNC) or a base station controller (BSC), which supervises and coordinates various activities of the plural radio network nodes connected thereto. This type of connection is sometimes referred to as a backhaul connection. The RNCs are typically connected to one or more core networks.
Specifications for the Evolved Packet System (EPS) have been completed within the 3rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases. The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a variant of a 3GPP radio access technology wherein the radio network nodes are directly connected to the EPC core network rather than to RNCs. In general, in E-UTRAN/LTE the functions of an RNC are distributed between the radio network nodes, e.g. eNodeBs in LTE, and the core network. As such, the RAN of an EPS has an essentially “flat” architecture comprising radio network nodes connected directly to one or more core networks, i.e. they are not connected to RNCs. To compensate for that, the E-UTRAN specification defines a direct interface between the radio network nodes, this interface being denoted the X2 interface.
Device discovery is a well-known and widely used component of many existing wireless technologies, including ad hoc and cellular networks. Examples comprise Bluetooth and several variants of the IEEE 802.11 standards suite, such as WiFi Direct. The key technique used by these standards is to use specially designed beacon signals that devices broadcast so that nearby devices can detect the proximity of such beacon broadcasting devices. After having detected each other the devices may, if desired, initiate a communication session. This is typically done in a direct Device-to-Device (D2D) fashion, where the devices transmit data through direct signaling between each other.
During Release 12, the LTE standard has been extended with support of D2D, specified as “sidelink”, features targeting both commercial and Public Safety applications. Some applications enabled by Rel-12 LTE are device discovery, where devices are able to sense the proximity of another device and associated application by broadcasting and detecting discovery messages that carry device and application identities. Another application uses direct communication based on physical channels terminated directly between devices.
One of the potential extensions for the device to device work encompasses support of a Vehicle-to-everything (V2x) communication, which V2x communication includes any combination of direct communication between vehicles, pedestrians and infrastructure. V2x communication may take advantage of a Network (NW) infrastructure, when available, but at least basic V2x connectivity should be possible even in case of lack of coverage. Providing an LTE-based V2x interface may be economically advantageous because of the LTE economies of scale and it may enable tighter integration between communications with the NW infrastructure denoted Vehicle to Infrastructure (V2I) and Vehicle to pedestrian (V2P) and Vehicle to Vehicle (V2V) communications, as compared to using a dedicated V2x technology.
V2x communications may carry both non-safety and safety information for applications and services, where each of the applications and services may be associated with specific requirements sets, e.g., in terms of latency, reliability, capacity, etc.
ETSI has defined two types of messages for road safety: Co-operative Awareness Message (CAM) and Decentralized Environmental Notification Message (DENM).
CAM: The CAM message is intended to enable vehicles, including emergency vehicles, to notify their presence and other relevant parameters in a broadcast fashion. Such messages target other vehicles, pedestrians, and infrastructure, and are handled by their applications. CAM message also serves as active assistance to safety driving for normal traffic. The availability of a CAM message is indicatively checked for every 100 ms, yielding a maximum detection latency requirement of <=100 ms for most messages. However, the latency requirement for Pre-crash sensing warning is 50 ms.
DENM: The DENM message is event-triggered, such as by braking, and the availability of a DENM message is also checked for every 100 ms, and the requirement of maximum latency is <=100 ms.
The package size of CAM and DENM message varies from 100+ to 800+ bytes and the typical size is around 300 bytes. The message is supposed to be detected by all vehicles in proximity.
The Society of the Automotive Engineers (SAE) also defines a Basic Safety Message (BSM) for Dedicated Short Range Communication (DSRC) with various message sizes defined. According to the importance and urgency of the messages, the BSMs are further classified into different priorities.
With the current D2D specifications, it is necessary to transmit a Scheduling Assignment (SA) packet prior to the transmission of the actual data packet. The SA packet comprises information that allows the receiver to find and process correctly the data packet. Moreover, the SA information also indicates to a wireless device which radio resources are being used by other wireless devices. This information can be used by the wireless device to choose radio resources for its own transmission, i.e. distributed radio resource allocation. Not detecting scheduling assignments may lead to retransmissions of packets and also failed communications resulting in a limited or poor performance of the wireless communication network.